1. Field of the Invention
The present invention relates to a mobile station for use in mobile communications systems and the like. In particular, the invention is intended to reduce the signal loss occurring between an antenna and transmitter and receiver circuits.
2. Description of the Related Art
Usually, a cellular telephone set or the like has external connector terminals for connection to an external amplifier such as a booster or connection to an evaluation system for evaluating the performance of the cellular telephone set itself. Through the external connector terminal, the cellular telephone set can receive data from or supply data to such an external device.
As shown in FIG. 6 this type of conventional mobile station has a transmitter circuit 1 for processing a transmission signal, a receiver circuit 2 for processing a reception signal, a transmission/reception duplexer 5 for separating transmission waves and reception waves from each other, a transmission/reception antenna 8 that is connected to an antenna terminal 41, a reception antenna 9 that is connected to an antenna terminal 42, an input/output external connector terminal 10 an input external connector terminal 11, a switch 6 for selecting the transmission/reception antenna 8 or the input/output external connector terminal 10, and a switch 7 for selecting the reception antenna or the input external connector terminal 11.
In this mobile station, a signal that has been output from the transmitter circuit 1 is supplied to the transmission/reception antenna terminal 41 or the input/output external connector terminal 10 via the transmission/reception duplexer 5 and the switch 6. On the other hands a signal that has been received at the reception antenna terminal 42 or the input external connector terminal 11 is supplied to the receiver circuit 2 via the switch 7.
However, in the above conventional mobile station, large signal loss occurs particularly in its transmission side because the transmission/reception duplexer 5 and the switch 6 are interposed between the transmitter circuit 1 and the antenna terminal 41. Therefore, where the transmission power of the mobile station is determined, it is necessary to increase the output power of the transmitter 1 as much as the above signal loss, imposing an additional load on an amplifier in the transmitter circuit 1.